Some bearings are used in low-temperature and high-speed rotational environments such as in a liquid fuel turbo pump for a rocket engine or in a vacuum environment such as in space apparatus. Since these bearings cannot encapsulate a large amount of a fluid lubricant (grease), it is conceivable that a spacer having an oil reservoir for storing the lubricating oil is provided on the inner ring side of the bearing and the oil is then supplied with the help of the centrifugal force developed by the bearing being rotated. The applicant has suggested such a structure in a previous application (Japanese Patent Application No. 2010-227652).
On the other hand, disclosed in Patent Literature 1 is an angular ball bearing with a retainer riding on the inner circumferential surface of the outer ring, in which a lubricant supply mechanism is provided for supplying grease or the base oil of the grease to the guide surface of the inner circumferential surface of the outer ring in order to suppress grating noise, that is, the noise of the retainer in a low-speed operation region. Then, a grease reservoir in the shape of a circumferential groove is provided in the inner circumferential surface of the retainer so as to supply the base oil of the grease into between the retainer and the inner circumferential surface of the outer ring via through holes in the retainer (see FIGS. 9 to 13 in Patent Literature 1).
In Patent Literature 2, disclosed is a ball bearing which employs, as a grease reservoir, a space between the neighboring pockets of a retainer. The inner and outer circumferential surfaces of the retainer are provided with the surface lay in the circumferential direction, so that the base oil separated from the grease retained in the grease reservoir is allowed to flow and to be supplied along the surface lay onto the surface of each of the rolling elements.